Powered surgical instruments are often used in surgical procedures such as orthopedic surgery. The surgical instruments can be of many types such as a rotary drill, reamer, wire driver, sagittal saw, oscillating saw, reciprocating saw, ultrasonic device, etc. Typically, the surgical instrument includes a housing or a shell. The housing holds the tool power generating components that outputs the energy applied to the surgical site. The tool may be a drill bit, bur, saw, ultrasonic cutting or cauterizing tip, etc. An energy application, such as a drill bit, a saw blade, a bur, an electrode or ultrasonic tip extends forward from the housing.
Some powered surgical tools are energized by a battery that is attached to the housing. Typically the battery includes its own case or housing. One or more rechargeable cells are disposed in the battery housing. A battery for charging this type of tool is disclosed in the Applicant's PCT App. No. PCT/US2012/064764 published as US Pat. Pub. No. 2014/0266057, the contents of which are explicitly incorporated herein by reference.
The use of a battery eliminates the need to provide a power cord connected to an external power source. The elimination of the power cord offers several benefits over corded surgical instruments. Surgical personnel using this type of instrument do not have to concern themselves with either sterilizing a cord so that it can be brought into the sterile surgical field surrounding the patient or ensuring that, during surgery, an unsterilized cord is not inadvertently introduced into the surgical field. Moreover, the elimination of the cord results in the like elimination of the tripping and tangling hazard, physical clutter, and field-of-view blockage that the cord otherwise brings to a surgical procedure. Specifically, when pulled or tangled during the surgical procedure, the cord can become unsterilized, can be pulled from the hands of the user, and can be fully or partially disconnected from a power socket thereby ceasing operation of the instrument and/or creating a potential for electrically shocking the patient. Also, the cord is prone to increased failure relative to other components of the instrument when subjected to steam sterilization, such as with an autoclave.
A powered surgical tool also includes a manually actuated switch or trigger. The practitioner using the tool actuates this switch to control both the on/off state and the operating state of the tool. The state of the trigger is monitored by a control circuit. If the tool is battery powered, this control circuit is typically in the tool housing. It is however known at least in the field of non-surgical tools to place this controller in the battery housing. Based on the state of the trigger this control circuit selectively applies energization signals from the cells integral with the battery to the tool power generating circuit. The control circuit thus controls the energization of the tool power generating circuit. The inventors' Assignee's U.S. Pat. No. 7,638,958, the contents of which are incorporated herein by reference discloses one such battery powered surgical tool.
The battery powered motorized surgical tools used today are relatively large in mass, 1.3 kg or more including the battery. The motors internal to these tools tend to output a minimum of 125 Watts of power. These tools are used for applications where significant amounts of power are required. These applications include large bone resection and removal procedures as part of knee or hip replacement procedure. These tools are also used for drilling and reaming bores into large bone such as femur.
Available battery powered surgical tools generally work well for the purposes for which they are intended. However, to date, it has proven difficult to provide a motorized battery powered motorized surgical tool that outputs power in the range of 25 to 125 Watts. These tools are used for such applications where a relatively small application of power is required in order to perform a delicate task. These types of procedures include osteotimies and fracture fixations. Typically these tools weight 150 grams or less. Many of these tools being small in size are elongated in structure, shaped like an oversized pen or pencil. This allows the practitioner holding the tools to hold the tool like pencil. This allows the practitioner to by moving the thumb and forefinger, precisely position the tools so that the tool can perform the desired task.
One reason that it is difficult to provide this type of battery powered tool is that it has proven difficult to provide package the components forming the tool as well as the attached battery, in a unit the practitioner can, with minimal strain hold between the thumb and forefinger.